Re: Linguist 13:2096
Actually the journalist seems to have confused motor-articulatory
disabilities and expressive agrammatism (not agrammaticism), a
technical term that indicates a severe speech disturbance caracterized
by omission of main verbs and function words and highly impaired
syntax. However in the original Lai et al.'s work (A forkhead-domain
gene is mutated in a severe speech and language disorder. Lai et
al. Nature (2001) 413:519) and in the review of this paper by Andrew
(S Andrew, Communicating a new gene vital for speech and
language.Clinical Genetics. (61) 2002, 97-100), there is not such
confusion between agrammatism and motor-articulatory abilities:
"The family crucial to this paper presented with the inability to
break words up into subunits, difficulties with grammar and expressive
language as well as defects in the fine orofacial movements required
for articulation. Affected individuals have such severe dyspraxia
that their speech is almost incomprehensible ... Brain imaging studies
suggested abnormalities in the cortical and subcortical areas of the
frontal lobe, in particular the basal ganglia. ..." (Andrew 2002).
The studied family would miss FOXP2 gene, that for these reasons has
been linked to language faculty. It is interesting to note that the
reported abnormalities probably due to this missing gene concern
frontal lobe and basal ganglia, i.e. fronto-striatal circuits that are
thought to be essential in verbs production (SF Cappa et al., Object
and action naming in Alzheimer's disease and frontotemporal dementia,
Neurology, Vol. 50, 351-355, 1998; A Daniele et al., Evidence for a
possible neuroanatomical basis for lexical processing of nouns and
verbs, Neuropsychologia, 32, 1325-1341, 1994).
A genetic mutation as the basis for language origin had been
hypothesized by T Crow 2000a (TJ Crow. Schizophrenia as the price that
Homo sapiens pays for language: a resolution of the central paradox in
the origin of the species. Brain Research Reviews, (31) 2000,
118-129) as a factor of hemispheric specialization. Crow 2000b is more
precise on the causes of genetic mutation: "the critical change (a
"saltation") in the transition from a precursor hominid to modern Homo
sapiens occurred in a gene for cerebral lateralisation located on the
Y chromosome in a block of sequences that had earlier transposed from
the X. Sexual selection acting upon an X-Y homologous gene to
determine the relative rates of development of the hemispheres across
the antero-posterior axis ("cerebral torque") allowed language to
evolve as a species-specific mate recognition system...." (Timothy
J. Crow (2000) Did Homo Sapiens Speciate on the y Chromosome?.
Psycoloquy: 11(001).
Giancarlo Buoiano
Neuroscience Dpt.
Univ. of Pisa